Production of reduced catalyst PDC via gradient driven reactivity

ABSTRACT

A method of forming a PDC cutter having solvent metal catalyst located adjacent the diamond and/or in the diamond and a layer of reactive material on the layer of diamond, the layer of reactive material for promoting the flow of the solvent metal catalyst material from the layer of diamond under high pressure and high temperature.

TECHNICAL FIELD

The present invention, in several embodiments, relates generally topolycrystalline diamond compact (PDC) cutters and methods of making PDCcutters for rotary drag bits for drilling subterranean formations.

BACKGROUND

Rotary drag bits have been used for subterranean drilling for manydecades, and various sizes, shapes and patterns of natural and syntheticdiamonds have been used on drag bit crowns as cutting elements. In manyformations, a drag bit can provide an improved rate of penetration (ROP)of the drill bit during drilling over the ROP of a tri-cone drill bit.

Over the past few decades, rotary drag bit performance has been improvedwith the use of a polycrystalline diamond compact (PDC) cutting elementor cutter, comprised of a planar diamond cutting element or table formedonto a tungsten carbide substrate under high temperature and highpressure conditions. The PDC cutters are formed into a myriad of shapesincluding, circular, semicircular or tombstone, which are the mostcommonly used configurations. Typically, the PDC diamond tables areformed so the edges of the table are coplanar with the supportingtungsten carbide substrate. Bits carrying PDC cutters, which forexample, may be brazed into pockets in the bit face, pockets in bladesextending from the face, or mounted to studs inserted into the bit body,have proven very effective in achieving a high rate of penetration (ROP)in drilling subterranean formations exhibiting low to medium compressivestrengths. The PDC cutters have provided drill bit designers with a widevariety of improved cutter deployments and orientations, crownconfigurations, nozzle placements and other design alternativespreviously not possible with the use of small natural diamond orsynthetic diamond cutters. While the PDC cutting element improves drillbit efficiency in drilling many subterranean formations, the PDC cuttingelement is nonetheless prone to wear when exposed to certain drillingconditions, resulting in a shortened life of a rotary drag bit.

PDC cutters comprise combining synthetic diamond grains with a suitablesolvent catalyst material to form a mixture. The mixture is subjected toprocessing conditions of extremely high pressure/high temperature (HPHT)where the solvent catalyst material promotes desired inter-crystallinediamond-to-diamond bonding between the grains, thereby forming a PDCstructure. The resulting PDC structure has enhanced properties of wearresistance and hardness. PDC materials are useful in aggressive wear andcutting applications where high levels of wear resistance and hardnessare desired. The cutting elements used in such earth-boring tools ofteninclude polycrystalline diamond compact (often referred to as “PDC”)cutting elements, which are cutting elements that include cutting facesof a polycrystalline diamond material. Polycrystalline diamond materialis material that includes inter-bonded grains or crystals of diamondmaterial. In other words, polycrystalline diamond material includesdirect, inter-granular bonds between the grains or crystals of diamondmaterial. The terms “grain” and “crystal” are used synonymously andinterchangeably herein.

PDC cutters typically include a metallic substrate material that isjoined to a layer or body of the PDC material during the same HPHTprocess that is used to form the PDC body. The metallic substratefacilitates attachment of the PDC cutter to a drill bit. Techniques areused to improve the wear resistance of the PDC cutter which is known tosuffer thermal degradation at a temperature starting at about 400° C.and extending to 1200° C. Conventional PDC cutters are known to havepoor thermal stability when exposed to operating temperatures above 700°C. Some of the techniques for improving wear resistance of a PDC cutterare directed to improving the thermal stability of the PDC cutter. Onetechnique of improving thermal stability of a PDC cutter is to leach theuppermost layer of PDC cutter to remove substantially all solvent metalcatalyst material from the PDC cutter surface while retaining as muchmetal catalyst material in the remaining portion of the PDC cutter.

While this technique improves the thermal stability of the treateduppermost layer of a PDC cutter, such a PDC cutter tends to suffer fromspalling and de-lamination during use.

Therefore, it is desirable to provide a PDC cutter having improved wearresistance properties and thermal stability which reduces or minimizesspalling and de-lamination of the PDC cutter without leaching theuppermost layer of the PDC cutter to remove solvent metal catalystmaterial from the PDC cutter.

BRIEF SUMMARY

A PDC cutter having solvent metal catalyst material in the diamond andmethods of manufacture thereof.

The advantages and features of the present invention will becomeapparent when viewed in light of the detailed description of the variousembodiments of the invention when taken in conjunction with the attacheddrawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of a PDC compact before pressing;

FIG. 1A is a drawing of various patterns for interfacial barrier designsfor the control of catalyst migration to the diamond powder and sink;

FIG. 2 is a drawing of the PDC of FIG. 1 after pressing;

FIG. 3 is a drawing of another embodiment of the present invention of aPDC compact before pressing;

FIG. 4 is a drawing of another embodiment of the present invention ofthe PDC of FIG. 3 after pressing;

FIG. 5 is a drawing of another embodiment of the present invention of aPDC compact before pressing;

FIG. 6 is a drawing of another embodiment of the present invention of aPDC compact before pressing;

FIG. 7 is a drawing of another embodiment of the present invention of aPDC compact before pressing; and

FIG. 8 is a drawing of another embodiment of the present invention of aPDC compact before pressing.

DETAILED DESCRIPTION

Illustrated in FIG. 1 is a representation of a compact 10 to be pressedunder high pressure and high temperature (HPHT) to form apolycrystalline diamond compact (PDC) for use as a cutter on a rotarydrag bit. The compact 10 includes a substrate 14, layer of eitherpowdered solvent catalyst 15 or a solid disc of catalyst 15, a firstlayer of diamond powder 12, a sacrificial layer or second layer 12′ ofdiamond powder, and a sink 16. The compact 10 includes two layers ofdiamond powder, a first layer of diamond powder 12 typically having aparticle size in the range of about 5 microns to about 40 microns and asecond, more coarse sacrificial layer 12′ of diamond powder havingparticle size in the range of about 100 microns to about 500 microns ormulti-modal particle size distributions thereof for forming a diamondtable for cutting. The layer of powdered solvent catalyst 15, such ascobalt, while illustrated as a separate layer of powdered cobalt, may bemixed within primarily the powdered diamond 12, if desired. Thesacrificial layer 12′ of diamond powder acts as a catalyst for formingthe diamond table and for attaching the polycrystalline diamond table toa substrate 14. The substrate 14 typically comprises a cermet material(i.e., a ceramic-metal composite material) such as, for example,cobalt-cemented tungsten carbide for forming a backup substrate, afterpressing. The sink 16 acts as a getter that can react favorably with oradsorb any catalyst, or any suitable metal catalyst, in the diamondpowder 12 and in the sacrificial layer 12′ of diamond powder to reducethe concentration of the catalyst, or other suitable metal catalyst, inthe diamond powder 12, which may be swept into the diamond grains ofdiamond powder 12 from either the substrate 14, or the layer of powdersolvent catalyst 15, or solid catalyst disc 15, during sintering. Duringsintering, each of substrate 14 and the layer of catalyst 15 serves ascatalyst material for forming the inter-granular diamond-to-diamondbonds and, the resulting diamond table, from the diamond grains. Inother methods, a layer of powdered catalyst material 15, or any suitablemetal catalyst material 15, may additionally be mixed with the diamondgrains prior to sintering in an HTHP process. Upon formation of adiamond table 12 using an HTHP process, catalyst material may remainafter pressing and cooling to form a diamond microstructure for thediamond table 12 of the compact 10. The sacrificial layer 12′ maycomprise coarse diamond, carbide, graphite, ceramic, metal, or anysuitable mixtures thereof as well as any suitable materials that promotefracturing of the sacrificial layer 12′ and allow the migration ofcatalyst 15 therethrough. The sink 16 may be any suitable material suchas fine diamond, graphite, metals, or metal alloys that will react ator, preferably, above the reactivity level of the diamond powder 12. Byplacing the sink 16 over the diamond powder 12 and sacrificial layer12′, the sink 16 causes a solvent gradient to occur across the diamondpowder 12 and sacrificial layer 12′ for the solvent catalyst 15 in thediamond powder 12 and sacrificial layer 12′ to migrate to the sink 16during high pressure and high temperature formation of the compact 10.The sacrificial layer 12′ of diamond powder acts as a sacrificial layerto be removed after the High Pressure High Temperature (HPHT) portion ofthe process by any suitable means, such as direct separation of thesacrificial layer 12′ of diamond powder from diamond layer 12 or cuttingor grinding, or lapping, etc. The sacrificial layer 12′ of diamondpowder should not remain on the compact 10, although in some instancesit may be retained. While coarse diamond powder for the sacrificiallayer 12′ is preferred to be used, any diamond powder may be used andmay include a minimally reacting material therein, if so desired. Thesacrificial layer 12′ of coarse diamond powder may be in powder form,mixed with a suitable metal, layered, or in any combination thereof. Thesacrificial layer 12′ of diamond powder should react minimally with thediamond powder layer 12 allowing the catalyst to pass freely through thesacrificial layer 12′ of diamond powder with minimal reactivitytherewith and should be easily removable from the diamond powder layer12. In certain instances, the sacrificial layer 12′ of diamond powdermay not be used and only the solvent catalyst layer 15 used, if thesolvent catalyst layer 15 may be easily separated from the powdereddiamond layer 12 and the solvent catalyst layer 15 retains the activitythereof without the sacrificial layer 12′ of diamond powder after hightemperature and high pressure formation of the compact 10.

As illustrated in FIG. 1A, if desired, the layer 15 may consist of asolid metal disc 15 or metal alloy disc 15 having reduced catalyticactivity, such as a nickel disc 15. The disc 15 includes a plurality ofapertures 18 therein to control the migration of catalyst containedwithin the substrate 14 into the diamond layer 12 and sacrificial layer12′ to the sink 16. The thickness of the disc 15, or layer of powderedcatalyst 15, may be any thickness in the range of approximately 1 micronto approximately 100 microns. The shape of the apertures 18 may be anydesired shape, such as circular, square, rectangular, oval, ellipsoid,triangular, or any desired combinations thereof in any desired patternsthereof. The length and width of the apertures 18 may be any desireddiameter thereof or length and width thereof convenient for the size ofthe compact 10. The apertures 18 may have any desired pattern, such assymmetrical, asymmetrical, any desired combinations thereof, etc.

Referring back to FIG. 1, the initial concentration of the solventcatalyst 15 below diamond powder 12 or in the diamond powder 12 isillustrated by the graphic representation of 15′ on the right side FIG.1, showing that the diamond powder 12 and sacrificial layer 12′ ofdiamond powder each have some concentration of solvent catalyst 15therein while the highest concentration of solvent catalyst 15 is in thecatalyst layer 15 at or near the interface of the layer of diamondpowder 12. If desired, the wettability of the diamond powder 12 andsacrificial layer 12′ can be enhanced with a graphite coating or anyother agent to allow the catalyst 15 to migrate more easily to the sink16 from the diamond powder 12 and sacrificial layer 12′.

Illustrated in FIG. 2 is a representation of a compact 10 of FIG. 1, orwith the solid disc 15 of FIG. 1A, after high pressure and hightemperature pressing of the compact 10. As illustrated on the right sideof the compact 10, during high pressure and high temperature pressing ofthe compact 10, the affinity of the sink material 16 has caused thesolvent catalyst material 15 to migrate to the sink 16. As illustrated,the sink 16 has the highest concentration of the cobalt solvent catalyst15, after high pressure and high temperature pressing of the compact 10.As illustrated, the polycrystalline diamond table 12 formed from thediamond powder 12 and sacrificial layer 12′ of diamond powder includes,at or near the WC substrate 14, a first level 12A of concentration ofcatalyst material having a level of concentration of catalyst of abouttwo times or more of the level of concentration of catalyst in the WCsubstrate 14, a second level 12B of concentration of catalyst having alevel 12B of concentration of about the same level of concentration ofcatalyst as in the WC substrate 14, and a third level 12C ofconcentration of catalyst having a level 12C of concentration ofcatalyst decreasing from about the same level of concentration 12B ofcatalyst as in the WC substrate 14 to a minimum level of concentrationapproaching almost no catalyst in the diamond table 12 at the upper endor upper surface thereof, although the amount or concentration ofcatalyst is as minimal as required for formation of the diamond table 12of the compact 10. The level of concentration of catalyst in thesacrificial layer 12′ of coarse diamond powder 12′ is significantly lessthan that of the level of concentration of the catalyst in the WCsubstrate 14 with the sink 16 having a level of concentration ofcatalyst peaking at a level of about three times or more of the level ofconcentration of the catalyst, in the WC substrate 14. The solventcatalyst layer 15 may be deleted, if desired, when sufficient catalystmaterial from the substrate 14 is available during HPHT of the compact10. It will be appreciated that the volume or mass of the materialcomprising the sink 16 must be at least approximately equal to or largerthan the volume or mass of catalyst material, such as from the catalystlayer 15 and any catalyst that may migrate from the substrate 14 that isto be to be removed from the diamond powder 12 and sacrificial layer 12′of diamond powder. Otherwise, the volume or mass of the sink 16 will notbe effective for the removal of the desired amount of catalyst materialfrom the layer of catalyst powder 15, or from a solid disc 15, from thelayer of diamond powder 12, and from sacrificial layer 12′ of diamondpowder.

Illustrated in FIG. 3 is another representation of an alternativeembodiment of the present invention where a compact 10 is to be pressedunder high pressure and high temperature to form a PDC for use as acutter on a rotary drag bit. The compact 10 includes a substrate 14, apowdered catalyst layer 15, a diamond powder layer 12, a sacrificiallayer or second layer 12′ of coarse diamond powder, and a sink orreactive layer 16. As illustrated, the compact 10 includes at least twolayers of diamond, one of diamond powder 12 (PDC FEED), typically havinga particle size of about 5 microns to about 40 microns, and another ofsacrificial layer 12′ of coarse diamond particles, typically having aparticle size of about 100 microns to about 500 microns, for forming adiamond table for cutting. A layer of powdered solvent catalyst 15, suchas cobalt powder, or a solid solvent catalyst disc 15, such as an ironand cobalt alloy disc, contacts the powdered diamond 12 for forming thediamond table from the diamond powder 12 and sacrificial layer 12′ ofdiamond powder and attaching the diamond table to a substrate 14, whichis formed from tungsten carbide powder for forming a backup substratefor the diamond table after pressing. The sink 16 acts as a getter thatcan react favorably with the cobalt solvent catalyst 15 to reduce theconcentration of the cobalt solvent catalyst 15 in the diamond powder 12and sacrificial layer 12′, after pressing and cooling to form thediamond microstructure of a diamond table 12 of the compact 10. The sink16 may be any suitable material, such as fine diamond, graphite, metals,or metal alloys that will react at or, preferably, above the reactivitylevel of the diamond powder 12. By placing the sink 16 over the tungstencarbide powder, the catalyst layer 15, the diamond powder layer 12, andsacrificial layer 12′, the sink 16 causes a solvent gradient to occuracross the tungsten carbide powder 14 for the cobalt solvent catalysttherein and the catalyst in the catalyst layer 15 to migrate to the sink16 during high pressure and high temperature formation of the compact10. Because the coarse diamond powder of the sacrificial layer 12′ has aparticle size in the range of about 100 microns to about 500 microns,the sacrificial layer 12′ will not strongly bond to the diamond layer 12at the interface therebetween during high pressure and high temperaturepressing. The overall permeability of the diamond layer 12 and thepermeability of the sacrificial layer 12′ of coarse diamond powder isdetermined by the mean free path of open porosity, which is formed bythe interstitial regions between individual grain boundaries betweengrains, and fractures that form under pressure and determines theeffectiveness at which any solvent catalyst migrates therethrough duringthe high pressure and high temperature process of forming the compact10, as the closed porosity of the diamond layer 12 and the closedporosity of the sacrificial layer 12′ of coarse porous diamond preventsany substantial migration of the catalyst 15 thereacross. When there isa greater amount of permeability in the diamond layer 12 andpermeability in the sacrificial layer 12′ of coarse porous diamondparticle layer, the solvent catalyst 15 will migrate through the diamondlayer 12 and the sacrificial layer 12′ of coarse porous diamond. If adiamond powder 12 is used that has a mean free path of open porositybelow the percolation threshold for the grain size distribution, thepermeability of the diamond layer 12 may be such that the catalyst 15cannot effectively migrate thereacross in any reasonable period of timefor the compact 10 formation process.

Illustrated in FIG. 4 is another representation of an alternativeembodiment of the present invention where a compact 10 is to be pressedunder high pressure and high temperature to form a PDC for use as acutter on a rotary drag bit. The compact 10 includes a substrate 14, alayer of powdered cobalt catalyst 15, a layer of diamond powder 12,another layer of coarse diamond powder 12′, and a sink 16 of finegraphite powder. The compact 10 includes at least two layers of diamond,one of diamond powder 12 having a particle size of about 5 microns toabout 40 microns and another of sacrificial layer 12′ of coarse diamondparticles having a particle size of about 100 microns to about 500microns for forming a diamond table for cutting. A layer of powderedcobalt solvent catalyst 15 contacts the powdered diamond 12 forattaching a diamond table to a substrate 14 formed from tungsten carbidepowder for forming a backup substrate for the diamond table formed fromthe diamond powder 12 and sacrificial layer 12′ of coarse diamondparticles having the diamond table secured thereto after pressing. Afine graphite powder, such as a sink 16, acts as a getter that can reactfavorably with the cobalt solvent catalyst 15 to reduce theconcentration of the cobalt solvent catalyst in the diamond powder 12,after pressing and cooling to form a diamond microstructure of a diamondtable of the compact 10. The fine crystalline graphite powder 16 willreact at or, preferably, above the reactivity level of the diamondpowder 12 (PCD FEED). By placing the sink 16 opposite the tungstencarbide powder for forming the substrate 14, the cobalt catalyst layer15, the diamond powder 12, and the sacrificial layer 12′ of coarsediamond powder, the sink 16 causes a solvent gradient to occur acrossthe tungsten carbide powder 14, the cobalt powder catalyst layer 15, thediamond powder layer 12 and the sacrificial layer 12′ for any cobaltsolvent catalyst to migrate to the sink 16 during high pressure and hightemperature formation of the compact 10. If desired, a solid solventcatalyst disc 15 may be placed between the diamond layer 12 and thesubstrate 14, rather than a layer of powdered cobalt catalyst 15. If thesacrificial 12′ of coarse porous diamond powder has an average particlesize in the range of about 100 microns to about 500 microns, thesacrificial layer 12′ of coarse porous diamond particle layer will notstrongly bond to the diamond layer 12 at the interface therebetween. Theoverall permeability of the diamond layer 12 and the permeability of thesacrificial layer 12′ of coarse diamond powder determines theeffectiveness at which any solvent catalyst migrates therethrough duringthe high pressure and high temperature process of forming the compact10, as the closed porosity of the diamond layer 12 and the closedporosity of the sacrificial layer 12′ of coarse diamond powder preventsor limits any migration of the catalyst 15 thereacross. When there isgreater permeability of the diamond layer 12 and the permeability of thesacrificial layer 12′ of coarse diamond powder, the solvent catalyst 15will migrate with greater effectiveness through the diamond layer 12 andthe sacrificial layer 12′ of coarse diamond powder. If a diamond powder12 is used that has a mean free path of open porosity below thepercolation threshold for the grain size distribution, the permeabilityof the diamond layer 12 may be such that the solvent catalyst 15 cannoteffectively migrate thereacross in any reasonable period of time for thecompact formation process.

Illustrated in FIG. 5 is another representation of an alternativeembodiment of the present invention where a compact 10 is to be pressedunder high pressure and high temperature to form a PDC for use as acutter on a rotary drag bit. The compact 10 includes a substrate 14, alayer of diamond powder 12, a small or thin sacrificial layer of coarsediamond powder 12′, when compared to the thickness of the layer 12 ofdiamond powder, and a reactive sink layer 16. The compact 10 includes atleast two layers of diamond, one of diamond powder 12, typically havinga particle size of about 5 microns to about 40 microns, and another ofsacrificial layer 12′ of coarse diamond powder, typically having aparticle size of about 100 microns to about 500 microns that are usedfor forming a diamond table for cutting. A powdered solvent catalyst,such as cobalt powder, is mixed with the diamond powder 12. Asacrificial layer 12′ of coarse diamond powder is for forming thediamond table from the diamond powder 12 and sacrificial layer 12′ ofcoarse diamond powder and attaching the diamond table to a substrate 14formed from tungsten carbide powder for forming a backup substrate forthe diamond table after pressing. A sink 16 (a reactive layer) acts as agetter that can react favorably with any cobalt solvent catalyst toreduce the concentration of the cobalt solvent catalyst in the diamondpowder 12 and sacrificial layer 12′ of diamond powder after pressing andcooling to form a diamond microstructure of a diamond table 12 of thecompact 10. The sink 16 may be any suitable material such as finediamond, graphite, metals, or metal alloys that will react at or,preferably, above the reactivity level of the diamond powder. By placingthe sink 16 opposite the tungsten carbide powder of the substrate 14,diamond powder 12, the sacrificial layer 12′ of coarse diamond powder,the sink 16 causes a solvent gradient to occur across the diamond powderlayer 12 (PCD FEED) having cobalt solvent catalyst therein for thecobalt solvent catalyst to migrate to the sink 16 during high pressureand high temperature formation of the compact 10. Because thesacrificial layer 12′ of coarse diamond powder has a particle size inthe range of about 100 microns to about 500 microns, the sacrificiallayer 12′ of coarse porous diamond particle layer 12′ will not stronglybond to the diamond layer 12 at the interface therebetween. The overallpermeability of the diamond layer 12 and the permeability of thesacrificial layer 12′ of diamond powder determines the effectiveness atwhich the solvent catalyst migrates therethrough during the highpressure and high temperature process of forming the compact 10 as theclosed porosity of the diamond layer 12 and the closed porosity of thesacrificial layer 12′ of coarse diamond powder prevents any substantialmigration of the catalyst thereacross. When there is a large amount ofpermeability in the diamond layer 12 and permeability in the sacrificiallayer 12′ of coarse diamond powder, any solvent catalyst in the diamondpowder 12 will migrate with a greater effectiveness through the diamondlayer 12 and the sacrificial layer 12′ of coarse diamond powder. If adiamond powder 12 or a sacrificial layer 12′ of coarse diamond powder isused that has mean free path of open porosity below the percolationthreshold for the grain size distribution, the permeability of thediamond layer 12 and the sacrificial layer 12′ may be such that thecatalyst cannot effectively migrate thereacross in any reasonable periodof time for the compact formation process.

Illustrated in FIG. 6 is another representation of an alternativeembodiment of the present invention where a compact 10 is to be pressedunder high pressure and high temperature to form a PDC for use as acutter on a rotary drag bit. The compact includes a substrate 14, acatalyst layer 15, a layer of powdered diamond 12, a sacrificial layer12′ of diamond powder extending around the top surface and circumferenceof the layer of powdered diamond 12, extending around the circumferenceof the catalyst layer 15, and extending around the circumference of thesubstrate 14, and a reactive layer forming a sink 16 extending over thetop or upper surface and over or around the entire circumference of thesacrificial layer 12′ of diamond powder. The compact 10 includes atleast two layers of diamond, one of diamond powder 12, typically havinga particle size of about 5 microns to about 40 microns, and another ofsacrificial layer 12′ of coarse diamond powder, typically having aparticle size of about 100 microns to about 500 microns, for forming adiamond table for cutting, each layer 12 and 12′ extending around aportion of the tungsten carbide powder 14. A layer of powdered solventcatalyst 15, such as cobalt powder, or solid solvent catalyst disc 15,such as an iron and cobalt alloy disc, contacts the substrate 14 andcontacts the powdered diamond 12 for forming the diamond table from thediamond powder 12 and sacrificial layer 12′ of diamond powder andattaching the diamond table to a substrate 14 formed from tungstencarbide powder for forming a backup substrate for the diamond tableafter pressing. A sink or reactive layer 16 extends around the diamondlayers 12 and 12′ as well as the tungsten carbide powder 14 with thesink or reactive layer 16 acting as a getter that can react favorablywith the solvent catalyst 15 to reduce the concentration of the solventcatalyst in the diamond powder 12 and sacrificial layer 12′ of coarsediamond powder after pressing and cooling to form diamond microstructureof a diamond table 12 of the compact 10. The sink may 16 be any suitablematerial such as fine diamond, graphite, metals, or metal alloys whichwill react at or, preferably, above the reactivity level of the diamondpowder. By placing the sink 16 opposite and around the diamond powder 12and sacrificial layer 12′ of diamond powder, the sink 16 causes asolvent gradient to occur across the tungsten carbide powder 14 thediamond powder 12, and the sacrificial layer 12′ for any solventcatalyst 15 to migrate to the sink or reactive layer 16 during highpressure and high temperature formation of the compact 10. Because thecoarse diamond powder 12′ has a particle size in the range of about 500microns to about 1000 microns, the sacrificial layer 12′ of coarsediamond powder will not strongly bond to the diamond layer 12 at anyinterface therebetween. The overall permeability of the diamond layer 12and the permeability of the sacrificial layer 12′ of coarse diamondpowder determines the effectiveness at which solvent catalyst 15migrates therethrough during the high pressure and high temperatureprocess of forming the compact 10 as the closed porosity of the diamondlayer 12 and the closed porosity of the sacrificial layer 12′ of coarsediamond powder prevents any substantial migration of the solventcatalyst 15 thereacross. When there is a large amount of permeability inthe diamond layer 12 and permeability in the sacrificial layer 12′ ofcoarse diamond powder, the solvent catalyst 15 will migrate with greatereffectiveness through the diamond layer 12 and the sacrificial layer 12′of coarse diamond powder. If a diamond powder 12 and/or sacrificiallayer of coarse diamond powder 12′ is used that has a mean free path ofopen porosity below the percolation threshold for the grain sizedistribution, the permeability of the diamond layer 12 and/or thesacrificial layer 12′ of coarse diamond powder may be such that thecatalyst 15 cannot effectively migrate thereacross in any reasonableperiod of time for the compact formation process.

Illustrated in FIG. 7 is another representation of an alternativeembodiment of the present invention where a compact 10 is to be pressedunder high pressure and high temperature to form a PDC for use as acutter on a rotary drag bit. The compact 10 includes a substrate 14, acatalyst layer 15, a layer of diamond powder 12 (PCD FEED), and areactive layer forming a sink 16. The compact 10 includes a layer ofdiamond powder 12, typically having a particle size of about 5 micronsto about 40 microns, for forming a diamond table for cutting. A powderedsolvent catalyst 15, such as cobalt powder, extends around the diamondpowder 12 on all sides thereof including the circumference thereof andan upper portion of the tungsten carbide powder 14 for forming a backupsubstrate for 14 the diamond table after pressing. A sink or reactivelayer 16 extending around the upper surface and circumference of thepowdered solvent catalyst layer 15, and a portion of the tungstencarbide powder 14. The sink or reactive layer 16 acts as a getter thatcan react favorably with the solvent catalyst 15 to reduce theconcentration of the solvent catalyst 15 in the diamond powder 12 afterpressing and cooling to form diamond microstructure of a diamond table12 of the compact 10. The sink may be any suitable material such as finediamond, graphite, metals, or metal alloys which will react at or,preferably, above the reactivity level of the diamond powder. By placingthe reactive sink layer 15 around the solvent catalyst 15 and thetungsten carbide powder 14, the sink causes a solvent gradient to occuracross the tungsten carbide powder 14 for the any solvent catalyst 15 tomigrate to the sink 16 during high pressure and high temperatureformation of the compact 10. The overall permeability of the diamondlayer 12 determines the effectiveness at which the solvent catalystmigrates therethrough during the high pressure and high temperatureprocess of forming the compact 10 as the closed porosity of the diamondlayer 12 prevents any substantial migration of the solvent catalyst 15thereacross. When there is a large amount of permeability in the diamondlayer 12, the solvent catalyst 15 will migrate with greatereffectiveness through the diamond layer 12. If a diamond powder 12 isused that has a mean free path of open porosity below the percolationthreshold for the grain size distribution, the permeability of thediamond layer 12 may be such that the solvent catalyst 15 cannoteffectively migrate thereacross in any reasonable period of time for thecompact formation process.

Illustrated in FIG. 8 is another representation of an alternativeembodiment of the present invention where a compact 10 is to be pressedunder high pressure and high temperature to form a PDC for use as acutter on a rotary drag bit. The compact 10 includes a substrate 14, alayer of diamond powder 12, a layer of powdered catalyst 15 contactingthe layer of diamond powder 12 on the top side and circumference thereofand an upper portion of the substrate 14, and a reactive layer forming asink 16. The compact 10 includes a layer of diamond powder 12 (PCDFEED), typically having a particle size of about 5 microns to about 40microns, for forming a diamond table for cutting, a powdered solventcatalyst 15, such as cobalt powder extending around the diamond layer 12on the upper surface thereof and around the circumference and an upperportion of the tungsten carbide powder 14, any desired amount, forforming the diamond table from the diamond powder 12 and attaching thediamond table to a substrate 14 formed from tungsten carbide powder forforming a backup substrate for the diamond table after pressing. A sinkor reactive layer 16 extending around the solvent catalyst layer 15, anda portion of the tungsten carbide powder 14, any desired amount, actingas a getter that can react favorably with the solvent catalyst 15 aroundthe diamond powder layer 12 and any solvent catalyst in the substrate 14to reduce the concentration of the solvent catalyst 15 in the diamondpowder 12 after pressing and cooling to form diamond microstructure of adiamond table 12 of the compact 10. The sink 16 may be any suitablematerial such as fine diamond, graphite, metals, or metal alloys whichwill react at or, preferably, above the reactivity level of the diamondpowder 12. By placing the sink 16 around the diamond powder 12 and thesubstrate 14, the sink 16 causes a solvent gradient to occur across thetungsten carbide powder of the substrate 14 for any solvent catalyst 15to migrate to the sink 16 during high pressure and high temperatureformation of the compact 10. The overall permeability of the diamondlayer 12 determines the effectiveness at which the solvent catalyst 15migrates through the diamond powder 12 during the high pressure and hightemperature process of forming the compact 10 as the closed porosity ofthe diamond powder of the layer 12 prevents any substantial migration ofthe catalyst thereacross. When there is a large amount of permeabilityin the diamond powder layer 12, any solvent catalyst 15 will migratewith greater effectiveness through the diamond layer 12. If a diamondpowder 12 is used that has a mean free path of open porosity below thepercolation threshold for the grain size distribution, the permeabilityof the diamond powder layer 12 may be such that the catalyst cannoteffectively migrate thereacross in any reasonable period of time for thecompact formation process.

While particular embodiments of the invention have been shown anddescribed, numerous variations and alternative embodiments will occur tothose skilled in the art. Accordingly, it is intended that the inventionbe limited in terms of the appended claims.

1. A method of making a compact comprising: depositing catalyst materialon a substrate; depositing diamond powder on the catalyst material;depositing a reactive material on the diamond powder, the reactivematerial formulated to remove catalyst from the diamond powder underhigh pressure and high temperature; and pressing and heating thereactive material, the diamond powder, the catalyst material, and thesubstrate to form a polycrystalline diamond compact from at least aportion of the diamond powder.
 2. The method of claim 1, whereindepositing a reactive material comprises depositing the reactivematerial opposite the substrate.
 3. The method of claim 1, whereindepositing diamond powder comprises: depositing a first diamond powderhaving a first particle size distribution on the substrate; anddepositing a second diamond powder having a second particle sizedistribution on the first diamond powder.
 4. The method of claim 3,further comprising removing the second diamond powder after forming thepolycrystalline diamond material.
 5. The method of claim 1, whereindepositing the reactive material comprises depositing one of finediamond, graphite, metal, and a metal alloy.
 6. The method of claim 1,wherein depositing the reactive material comprises depositingcrystalline graphite.
 7. The method of claim 3, wherein depositing thefirst diamond powder comprises depositing diamond particles having anaverage particle size within a range of from about 5 microns to about 40microns.
 8. The method of claim 7, wherein depositing the second diamondpowder comprises depositing second diamond particles having an averageparticle size within a range of from about 100 microns to about 500microns.
 9. The method of claim 3, wherein depositing the second diamondpowder comprises depositing diamond particles having multi-modalparticle size distribution.
 10. The method of claim 1, wherein thediamond powder comprises diamond particles and a wetting agent.
 11. Themethod of claim 1, wherein depositing the catalyst material comprisesdepositing cobalt powder.
 12. The method of claim 1, wherein depositingthe catalyst material comprises depositing a solid disc comprisingcobalt.
 13. The method of claim 1, wherein depositing the catalystmaterial comprises depositing the catalyst material to extend around aportion of the substrate.
 14. The method of claim 1, wherein depositingthe diamond powder comprises depositing the diamond powder to extendaround a portion of the substrate.
 15. The method of claim 1, whereindepositing the reactive material comprises depositing the reactivematerial to extend around a portion of the diamond powder.
 16. Themethod of claim 1, wherein depositing the reactive material comprisesdepositing the reactive material to extend around portions of each ofthe diamond powder and the substrate.
 17. The method of claim 1, whereinthe catalyst material has at least one aperture extending therethrough.18. The method of claim 1, wherein the catalyst material has a pluralityof apertures extending therethrough.
 19. A method of making a compactcomprising: depositing a catalyst material on a substrate; depositing afirst diamond powder on the catalyst material; depositing a seconddiamond powder on the first diamond powder; depositing a reactivematerial on the second diamond powder, the reactive material formulatedto remove catalyst from the first diamond powder and the second diamondpowder under pressure and temperature; and sintering the reactivematerial, the second diamond powder, the first diamond powder, thecatalyst material, and the substrate under high pressure and hightemperature to form a polycrystalline diamond compact from the firstdiamond powder.
 20. The method of claim 19, wherein the second diamondpowder comprises larger diamond particles than the first diamond powder.21. The method of claim 19, further comprising removing a materialformed from the second diamond powder after forming the polycrystallinediamond compact.
 22. The method of claim 19, wherein depositing thereactive material comprises depositing one of fine diamond, graphite,metal, and a metal alloy.
 23. A method of forming a polycrystallinediamond compact, comprising: forming a diamond layer over a substrate;forming a sacrificial layer on the diamond layer; forming a reactivelayer on the sacrificial diamond layer, the reactive layer comprising areactive material formulated to be more reactive with catalyst materialof the substrate than is a material of the diamond layer; performing asintering process to diffuse at least a portion of the catalyst materialinto each of the diamond layer, the sacrificial diamond layer, and thereactive layer and form a polycrystalline diamond compact from thediamond layer; and removing the reactive layer and the sacrificialdiamond layer after performing the sintering process.